RIYADH, Saudi Arabia - Saudi prosecutors sought the death penalty for five of 11 defendants charged with the murder of journalist Jamal Khashoggi, as their high-profile trial opened in Riyadh on Thursday.

The prosecution also said it was awaiting a response to two formal letters requesting evidence from Turkey, where Khashoggi was murdered inside the kingdom's Istanbul consulate on Oct 2 in a case that shocked the world.

All 11 accused were present with their lawyers at the first session of the trial, it said in a statement carried by the official Saudi Press Agency, without revealing their names or their alleged roles in the crime.

"The public prosecutor ... is seeking capital punishment for five of the defendants for their direct involvement in the murder," the statement said.

Five top Saudi officials - including royal court insider Saud al-Qahtani - have been sacked over Khashoggi's murder, but authorities have not said if they were among those charged.

Khashoggi, a Washington Post contributor, was murdered in what Riyadh called a "rogue" operation, tipping the kingdom into one of its worst diplomatic crises.

The 59-year-old Saudi insider-turned-critic was strangled and his body cut into pieces by a team of 15 Saudis sent to Istanbul for the killing, according to Turkish officials.

The whereabouts of Khashoggi's remains are still unknown. A Turkish television channel on Monday showed men carrying suitcases purportedly containing the remains into the residence of the Saudi consul general in Istanbul.

"The initial hearing for the 11 individuals indicted by the Public Prosecution in the case of the murder of citizen Jamal Khashoggi was held today ... in the Criminal Court of Riyadh," a statement from the Saudi prosecutor carried by SPA said.

Without naming them, the prosecutor said last November the five individuals facing by the death penalty were "charged with ordering and committing the crime".

SPA added that the defendants' lawyers attended the hearing and the court approved a request from the 11 for more time to prepare their defense. It gave no details on the next hearing.

The United Nations and human rights groups have called for an independent investigation into Khashoggi's killing.

The defense team on Thursday requested a copy of the charge sheet and a time frame within which to review the charges. The prosecution agreed to both requests while its investigation continues, SPA said.

No date has been set for the next hearing and it was unclear how long the trial would last.

"It is clear that elements from high levels of the Saudi state were involved in Khashoggi's murder," said H.A. Hellyer, senior associate fellow at the Royal United Services Institute.

"There is an immense amount of international interest in this trial, but also a lot of suspicion about whether those ultimately responsible for the crime will be held to account."

Afp - Reuters